Barnaby Joyce doesn't know if the baby his partner is carrying is his and he doesn't care.

Mr Joyce says he and Vikki Campion, his former media adviser, were not together during the time when she is estimated to have conceived.

Having previously asked for privacy and an end to scrutiny of his private life, Mr Joyce has now told Fairfax media the baby's paternity is "a grey area" and claims no one asked if it was his child - but he won't be getting a paternity test, he told Fairfax Media.

"It's mine, on the record, there it is," he said. "And can I say, even if it wasn't, I wouldn't care, I'd still go through this, I'd still love him."

The couple are expecting the baby in mid-April.

Mr Joyce's travel records show he claimed flights and expenses for several nights in Canberra and Sydney around mid-to-late July 2017.

The baby scandal involving the former deputy prime minister lost him his cabinet position and Nationals leadership.

"The matters that are in the papers today relating to Barnaby and Ms Campion are matters for them to resolve and I don't have any comments to make on it at all," he told reporters in western Sydney on Sunday.

Asked if Mr Joyce was derailing the government's agenda, Mr Turnbull replied: "The only rail that we're focused on today is the north-south rail link ... and believe me, that's the one the people of western Sydney are focused on."